Pneumatic tool



(No Model.)

J. BOYER. Y PNBUMTIC VToor..

Patented Nov. 5, 1895.

e im llullllllllllxllll ||l| NWN HHH m UNITED STATESl PATENT OFFICE.

JOSEPH BOYER, OF ST. LOUIS, MISSOURI.

PN EU MATIC Tool..

SPECIFICATION forming part of Letters Patent No. 549,102, dated November5, 1895.

Application filed August 10, 1895. Serial No. 558,840. (No model.)

To all whom it may concern,.-

Beit known that I, JOSEPH BOYER, a citi- Zen of the United States,residing at the city of St. Louis, in the State of Missouri, haveinvented a certain new and useful Improvement in Pneumatic Tools, ofwhich the following is a description, reference being had to theaccompanying drawings, forming part of this specification.

My invention has been illustrated in the accompanying drawings, and willhereinafter be described, as an improvement upon the tool recentlypatented to me by Letters Patent of the United States, No. 537 ,629,dated April 16, 1895; but the several features of my invention are notrestricted in their utility and application to that or any otherparticular tool, but may be employed to advantage in widely-differingtools, as will be apparent from the detailed description hereinaftergiven.

In the accompanying drawings, Figure lis a vertical longitudinal sectionof the complete tool approximately on the line l l of Fig. 3; Fig. 2, alongitudinal section of the pistonchamber and piston approximately onthe line 2 2 of Fig. 3; Fig. 3, a View of the rear end of the cylinderor piston-chamber, showing the position of the several ducts in the wallof the cylinder;l and Fig. 4 an enlarged vertical section of the Valve-chamber and valve with the valve in opposite position from that shownin Fig. l.

The same letters of reference are used to indicate identical parts inall the figures.

My invention may be said to consist in three features-first, novel meansrelating to the use of the pressure medium for giving the piston itsbackward or return stroke; second, in means for causing the tool to beautomatically thrown out of operation, even though the pressure-supplyis notI out off, whenever the cutting-tool is not in position to receivethe blow of the piston, and, third, in a novel throttle-valve forcontrolling the admission of the pressure-supply.

In the tool of my prior patent above referred to the piston was reset orgiven lits return stroke by means of a coiled spring confined in thefront end of the piston-chamber, the pressure-supply beingintermittently admitted only to the rear end of said chamber. Ihavefound it undesirable, however, to use such resetting-springs in tools oflarge size, and'in the tool of my present application I employ thepressure medium both for driving the piston forward to deliver its blowand for resetting it, and the feature of my invention relating theretowill be first described.

As in my prior tool, the cylinder or pistonchamber A has fitted againstits open rearv end a valve-block B, containing a valve-chamber and anautomatic valve controlling suitable ports, while fitted against therear side of said valve-block is a head-block or handlebase O, and thethree parts are secured together by means of a coupling-sleeve D,engaging a flange E upon the rear end of the cylinder and screwed at itsopposite end upon the head-block C. The block Gis formed integral withthe grasping-handle F, through which passes the inlet-duct G for thepressure-supply. The automatic valve is substantially the same inconstruction and operation as that in my prior tool and may beV brieflydescribed. The cylindrical Valve chamber formed in the block B is closedat its upper end by a plug H and at its lower end by a plug I, and inthe space between these two plugs is confined the waste-valve J. Theleft-hand or rear wall of the valve-chamber is provided with two ports,the upper being an inlet-port communicating with the pressure-su pplyduct G and the lowerbeing an exhaust-port communicating with theexhaust-duct K. When the valve is in its lower position, Fig. l, theinletport is closed and the exhaust-port open, and when it is moved toits upper position, Fig.v 4, the exhaust is closed and the inletopened.In both positions of the valve the port L in the front side of thevalve-chamber opening into the rear end of the piston-chamber remainsopen, this port being opposite the waist of the valve throughout thevalves movement. The waist of the valve is closed by a diaphragm at itsupper end, forming a chamber fitting over a central vertical extensionof the plug l, which closes the lower end of the valve-chamber, and thisplug and its extension have passing through them a duct M, communicatingwith the pressure-supply duct G, so that a constant pressure is admittedto the under side of the valve. The plug H at the upper end of the valvechamber has formed in its lower side a chamber N, the upper half ofwhich, of smaller diameter than the lower, is separated from the latterby a thin circular disk O, fitting against the shoulder formed by theenlarged lower half of the chamber and yieldingly held in position by acoiled spring confined in the lower half of the chamber and bearingagainst the disk. This disk constitutes a check-valve, which will yieldto pressure above it and permit such pressure to pass downward into thelower half of the chamber and act upon the upper side of the valve J andwhich will serve to confine such pressure in the chamber above the valveJ when the supply of pressure is cut off. Communicating with the upperhalf of the chamber N is a duct P, leading forward through the wall ofthe piston-chamber and opening into the latter bya port Q, whilecommunicating with the lower half of the chamber N beneath thecheck-valve is a second duct R, leading forward through the wall of thepiston-chamber and opening into the latter by a port at S, this latterduct and port being shown in dotted lines in Fig. l and in full lines inFig. 2. The pressure-supply, when admitted to the upper side of thevalve J thro ugh the duct P, acts upon a larger area of t-he valve thandoes the pressure admitted to the under side of the valve through theduct M and acting upon the diaphragm in the waist of the valve, so thatwhenever pressure is admitted to the upper side of the valve thepressure against the under side of the valve will be overcome and thevalve forced downward to the position in Fig. l, and as `the check-valveO will confine the pressure so admitted to the upper side of the valvethe latter will be held in its lower position until the pressure soholding it is permitted to escape through the exhaust-duct R, ashereinafter described, and as also fully explained in my prior patent.

The cylinder or piston-chamber A is bored to form two chambers ofdifferent diameters, the rear one T being the larger and the forward oneU the smaller. The piston consists of a long body V, fitting in thesmaller chamber U, and an enlarged but short head W, tting in the largerchamber T. A short distance from its front end the body V of the pistonis circumferentially grooved or cut away at X to form an annular chamberaround it, and communicating with this chamber by a port Y is a duct Y',connected at its front end to the duct M heretofore referred to, so thatpressure is admitted to said annular chamber whenever the latter standsopposite the port Y. This port will be closed body of the piston V atthe right of the space X whenever the piston is moved rearward towardits limit of stroke, and will be opened again when the piston is movedforward to deliver a blow to the tool. The pressure so admitted to thespace or chamber X will pass into the front end of the largepiston-chamber T, except when the piston is moved forward far enough, ashereinafter described, for the body of the piston at the left of thespace X to enter the rear end of the small piston-chamber and therebycut off any connection between the space X and the chamber T, as, forinstance, in Fig. 2.

Now t-he operation of the parts so far described is as follows: In Fig.l the piston is shown at nearly its forward limit of stroke, its extremefront end being' in contact with the rear end of the cutting or otherworking tool Z, which is fitted in the front end of the cylinder A, asusual. The valve J is in its lower position, with the inlet-port closedand the exhaust-port open, so that the pressure in the chamber T in rearof the piston is free to escape through the valve-chamber and eX- haustduct K. Assuming in Fig. l that the piston is still moving forwardinstead of starting backward, the contact of its front end with the endof the tool Z (the working or cutting end of the latter being in contactwith the object being operated upon), will arrest its forward movement,permitting the piston to move very slightly beyond the position shown inFig. l. The pressure admitted from the duct Y, through the port Y andspace X, to the front end ofthe piston-head W will start the pistonbackward. As soon as the piston has moved far enough for the body of thepiston at the right of the space X to pass and close the port Y, asbefore described, the admission of pressure to the front end of thechamber T will be cut oif, so that the further rearward movement of thepiston to its limit of stroke will be caused solely by the expansiveforce of the pressure already admitted to the chamber T and the momentumof the piston. At about the time or soon'after the piston reaches theposition in its backward movement which causes the port Y to be closedand admission of pressure to the chamber T cut off, as above described,the extreme forward end of the piston will clear and uncover the port S,forming the end of the exhaust-duct R, whereupon the pressure which hasbeen conned against the upper side of the valve J will be released andexhausted through said duct and port, and the pressure at the under sideof the valvewill throw the latter upward and close the exhaust-duct Kand open the inlet-port from the pressure supply-duct G, as in Fig. 4.The pressure supply will then be admitted to the rear end of the chamberT and act upon the piston to throw it forward to deliver its next blow.As soon as the piston has moved forward far enough for the rear end ofits head lV to clear the port Q, pressure will be admitted from thechamber T through said port and the duct P to the upper side of thecheck-valve O again and will pass the same and act upon the upper sideof the valve J and throw the latter downward to the position shown inFig. l, thereby again cutting off the pressure-supply and opening t theexhaust. The piston will be carried on forward by the diminishingpressure behind 1t and by its own momentum, against the rc- IOO IIO

sistance of the `pressure admitted from the duct Y', to the front end ofthe chamber T, until arrested by the contact of its front end with thetool Z, Fig. l, whereupon such pressure will again start the pistonbackward and the operationv above described be repeated. inasmuch as thelatter part of the forward stroke of the piston is effected by expandingor diminishing pressure behind it, aided by its own momentum, and isresisted by pressure admitted in front of the piston and acting upon asmall area thereof, it follows that the blow delivered to the tool willbe a quick elastic one, from which the piston will instantly rebound,much the same as where the piston is moved forward and completes itsstroke against the increasing resistance of a spring, as in the toolshown in my prior patent, and hence will produce less shock and jar thanwhere the piston strikes the tool a dead blow with the force of fullpressure behind it. So, too, inasmuch as the backward movement of thepiston is completed under the action of expanding pressure in the frontend of the chamber T, aided by its own momentum, this part of theoperation is much like that in my prior tool, where the piston is resetby the spring, whose pressurediminishes or ceases as the pistonapproaches its rearward limit of movement. The employment of the springin my prior tool produced an ease of action and caused an absence of theshock and jar common to tools of this character to a marked degree, andin my present tool, by the novel construction above described, l haveproduced a very similar action with the use of the pressure medium asthe resetting means.

It will be noticed that in the drawings the duct P is shown extendedforward of the port Q and opening at its extreme forward end into thesmall piston-chamber U by a port Q'. This is not essential, and the ductmay end at the port Q, as in the tool of my prior patent. The forwardextension here shown is provided for the purpose of preventing thepossibility of sufficient pressure passing from the front end of thechamber T to the upper side of the valve J at the beginning 4of theforward movement of the piston to force the valve J downward to itslower position, the extension of the duet and the port Q thus serving asa relief-passage from the front end of the chamber T, through which theair in front of the piston-head may escape at the beginning of theforward movement of the piston, as well as through the port A' and ductR and port S. Both the ports Q and S are closed by the front end of thepiston V soon after it begins its forward movement.

The second feature of my invention relates to the means forautomatically stopping the operation of the tool when the cutting orworking tool is removed from or not held in working position in thefront end of the cylinder. In the practical use rof these tools it isintended that the operator shall with his vhand which grasps the handleof the tool hold open the throttle-valve which controls the admission ofthe pressure-supply to the tool, and that the moment he quits using thetool and lays it down or releases his grasp upon the handle thethrottle-valve shall be automatically closed by the spring acting uponit and the pressure-supply be out off from the tool, so that the pistonwill cease to reciprocate. It has been found, however, that manyworkmen, to avoidthe necessity of maintaining a pressure of theirfingers or thumb upon the lever controlling the throttle-valve, will atthe beginning of work press said lever down to position to open thevalve and then tie it in such position, so that the pressure-supply willbe admitted to the tool until they again release the lever and allow thethrottle-valve to close. Owing to this practice among workmen, itfollows that the tool continues in constant operation from the time thethrottle-valve is first opened until it is finally permitted to close,no matter whether the tool is actively at work during a greater or lessportion of such time.

lt may frequently happen that the operator may lay the tool down atintervals in his work and leave it in full operation for considerableperiods of time, and thus subject it to much unnecessary wear. To guardagainst such misuse andabuse of tools of this character l have devisedmeans for automatically stopping the operation of the tool, or at leastso diminishing the stroke of the piston as to avoid any considerablewear and tear on the tool, whenever the cutting-tool is removed fromworking position in the front end of the cylinder. The means devised forthis purpose may be now described as follows:

In using tools of this character the operator with one hand holds thetool Z in position, while with the other he grasps the handle of thetool and holds it. Vhile the tool is at work, and the cutting end of thetool Z in contact with the object being operated upon, the pressureexerted upon the tool Z will maintain it in substantially the positionshown in Fig. l, instantly returning it thereto after each blow from thepiston. lf, however, the tool Z be removed, or the resistance offered toits forward movement be taken away, then the piston will be arrested atthe forward end of its stroke solely by the air in the front end of thechamber T, and consequently will move somewhat farther forward than itdoes when it contacts with the tool at work. In the movement of thepiston from its rearward to its forward position the valve J, as beforedescribed, is shifted to close the inlet-port and open the exhaust-portas soon as the rear end of the piston-head passes and opens the port Q,which admits pressure to the upper side of the valve and moves itdownward, and the pressure so admitted to the upper side of the valve isthere conned by the check-valve until at the return backward movement ofthe piston the exhaust- IOO IIO

port S is opened and the pressure permitted to escape. New it will beunderstood that if, instead of holding the pressure at the upper side ofthe valve J until it is permitted to exhaust through the port S, it bepermitted to exhaust at the end of the forward stroke of the piston, sothat the valve J will be then shifted and new pressure admitted to therear end of the chamber T, the piston, as it completes its forwardmovement and rebounds from contact with the tool e and the air in thefront end of the chamber T and begins its backward movement, will be metand arrested by the newly-admitted pressure in rear of it before it hasmoved but a slight distance rearward, and that it will thereupon bedriven forward again. *Now I have brought about this mode of operationby providin a second exhaust-passage from the upper side of the valve J,opening into thc chamber T at a point adapting it to be uncovered by thepiston when the latter makes what maybe termed an abnormal forwardstroke-that is, moved farther forward than it normally does when thetool-is at work. This exhaust may consist of a separate passageextending from the space at the upper side of the valve forward throughthe wall of the cylinder and opening into the piston-chamber at thepoint specified, or the same result may be accomplished by simplyproviding a short passage or port from the exhaust-duct R into thechamber, as shown at A'. Then the tool is at work, the piston isarrested in its forward movement at a point slightly beyond the positionshown in Fig. l, so that the port A' is not uncovered7 and the normaloperation of the tool heretofore described takes place; but when theresistance offered by the tool Z to further forward movement of thepiston is removed, and the piston moves forward far enough to uncoverthe port A', then the pressure at the upper side of the valve J, whichis holding the valve in its lower position, as in Fig. l, with theexhaust open and the inlet-port closed, will escape through the duct Rand port A' into the chamber T, and the pressure against the under sideof the valve J will thereupon lift the latter and close the exhaust Kand open the inlet-port and admit pressure to the rear end of thechamber T. A new supply of pressure will thus be admit-ted to thechamber T behind the piston while the latter is at the forward end ofthe chamber and prevent any considerable backward movement of it. Thepressure thus admitted to the chamber T will pass through the ports A'and Q and ducts R and P to the upper side of the valve J and throw thelatter downward again to the position shown in Fig. l, whereupon thepressure in the chamber T will escape and the valve be thrown upwardagain to admit a new supply of pressure to the chamber, and so on aslong as the piston remains in its extreme forward position with the portA' uncovered.

It will be understood that whenever the piston is moved forward of itsnormal position, so as to uncover the port A' and bring about theoperation above described, the body of the piston at the left of thespace X will enter the rear end of the small piston-chamber U andthereby cnt off the admission of the pressure from t-he duct Y' to thefront end of the chamber T, so that such pressure will not act upon thepiston-head XV to move the piston backward. There will, of course, besome pressure coniined in the front end of the piston-chamber after suchsupply from the duet Y' has been cut off, but this will gradually escapearound the piston, so that the latter will finally come to the positionshown in Fig. 2 and remain in substantially that position, with perhapsan exceedingly slight reciproeatin g movement, due to the rapidadmission and exhaust of pressure from the chamber T behind the piston,while the valve J continues its reciprocations,as above stated. Uponreinsertin g the tool Z in the end of the holder, as in Fig. 2, andforcing it inward until the piston is moved rearward far enough to closethe port A' and open communication between the d uct Y' and the frontend of the chamber T the normal operation of the machine, with fullreciprocations of the piston, will be immediately resumed.

From the foregoingl description it will be understood that if, with thethrottle-valve held open, the operator at any time lays down the tool orceases to hold it in working position the normal operation willimmediately cease, and that as soon as the cutting-tool is replacedand'put in workin g position the normal operation will be resumed. Sofar I am aware, this is an entirely new result in pneumatic tools, and Iam the first to accomplish it by any means or in any manner whatsoever.This feature of my invention, therefore, is of corresponding scope andis not limited beyond the terms of the respective claims relating to it.

The remaining feature of my invention relates to the novelthrottle-valve located in the handle of the tool for controlling theadmission of the pressure-supply to the tool. As seen in Fig. l, theduct G, through which the pressure supply is admitted, extends downwardand passes through the lower end of the handle by an enlarged threadedopening B', adapted for the reception vof the threaded nipple orcoupling upon the end of the iiexible tube through which thepressuresupply is conveyed to the tool. The duct G in its passagedownward through the handle is enlarged at two points to form twotransverse chambers C' D'. Extending upward into the handle from itslower end is a bore E', passing through the chambers C' D', whiletightly fitted in said bore is a tube or casing F', provided with portsG', opening into the chamber C', and ports H', opening into the chamberD'. Fitting in this tubular casing is a cylindrical valve I', having atits middle a reduced waist portion. Confined in the IOO IIO

IZO

lower end of the casingF is a coiled spring J', which yieldingly holdsthe valve I in the upper position shown, in which position it closes theports H, opening into the chamber D. Fitting in a narrow slot K', formedin the upper rear side of the handle, is a lever L', pivoted at M andprovided with a shoulder bearing upon the upper end of the valve I. Theupper end of this lever projects above the handle and is provided with athumbpiece II', by which it may be depressed into the slot K. XV hen sodepressed, the shoulder, bearing upon the upper end of the valve I',will press the latter downward against the resistance of the spring Jand open the ports H/, whereupon the pressure-supply admitted to thechamber D/ will pass through the ports H' and upward through the casingF, around the waist of the valve, and thence out through the ports Ginto the chamber C', and thence through the duct G to the tool. Uponreleasing the lever L the spring J will restore the valve to normalposition and cut off the pressure-supply. This automatic stopping of theoperation of the piston construction furnishes a very eflicient,easily-operated, and durable throttle-valve for controlling theadmission of pressure to the tool.

Having thus described my invention, I claiml. In a pneumatic tool, thecombination of a cylinder bored to form two piston chambers of differentdiameters, a pressure supply duct opening into the smaller chamber, apiston having an enlarged head fitting in the larger chamber and asmaller body portion fitting in the smaller chamber, said smallerportion being provided with ar depression or cut-away space so locatedas to furnish communication between the pressure supply duct and frontend of the larger piston chamber when the piston is in forward position,and to cut ofI:` such communication as the piston approaches rearwardposition, and an automatic valve for intermittently admitting pressureto and exhausting it from the larger chamber behind the piston-head,substantially as described.

2. In a pneumatic tool, the combination of the cylinder A bored to formthe two piston chambers, T and U, the piston having the enlarged head Wfitting in the chamber T, and the smaller body portion V iitting in thechamber U, the portion V of the piston being provided with the cut-awayspace X adapted to pass wholly or partly into and out of the chamber Tin the reciprocations of the piston, the duct Y' communicating with thepressure supply and opening into the chamber U opposite the space X, andan automatic valve for controlling the admission of pressure to auditsexhaust from the chamberT behind the piston-head WV, substantially asdescribed.

3. In a pneumatic toch-the combination,

ywith the piston and the working tool acted `upon by said piston, ofmeans controlled by said working tool for automatically throwing themachine out of normal operation when said tool is removed from workingposition.

4. In a pneumatic tool, the combination,

with the piston and the working tool acted upon by said piston, of meanscontrolled by said working tool for automatically throwing the machineout of normal operation when llf said tool is removed from workingposition and for causing it to resume normal operation when said tool isrestored to working position. l

5. In a pneumatic tool, the combination, with the piston and the workingtool whose shank receives the impact of the piston at the end of itsforwardstroke and aids in arresting and limiting the movement of thepiston, of means controlled by the posi tion of the piston forautomatically stopping the operation of the latter when, by the removalof the resistance offered by the working tool, it is permitted to exceedits normal forward limit of movement, for the purpose described.

6. In a pneumatic tool, the combination, with the piston and ports foradmitting pressure to the piston chamber in front 0f and behind thepiston, of means controlled by the position of the piston for cuttingoff the admission 'of pressure to the front end of the chamber andadmitting it to the rear end thereof when the piston exceeds its normalforward limit of movement, whereby when the piston is permitted toexceed such movement its reciprocation automatically ceases and it comesto rest in the front end of the piston chamber.

7. In a pneumatic tool, the combination, with the piston and the workingtool whose shank receives the impact of the piston at the end of itsforward stroke and aids in arresting and limiting the movement thereof,of means controlled by the position of the piston for admitting pressurebehind the piston when the latter, by the removal of the resistanceoffered by the working tool, is permitted to exceed its normal forwardlimit of movement, for the purpose described.

8. In a pneumatic tool, the combination, with the piston and the workingtool whose shank receives the impact of the piston at the end of itsforward stroke and aids in arresting and limiting the movement thereof,of means for cutting off the admission of pressure to the front of thepiston and admitting it behind the piston when the latter, by theremoval of the resistance offered by the working tool, is permitted toexceed its normal forward limit of movement, for the purpose described.

9. In a pneumatic tool/` having provision whereby when the pistons movedbeyond its normal forward limit of stroke it ceases to reciprocate andcomes to restin they front end of the piston chamber, the combination,with such piston and an automatic valve for controlling the admission ofpressure to the piston chamber, of the working tool whose shank normallyreceives the impact of the piston at IOO IIO

- NKA the end of its forward stroke, and means cooperating with thepiston and valve whereby when the piston is moved from the front end ofthe piston chamber by the insertion of the working tool in position itsoperation will be automatically restored.

l0. In a pneumatic tool, the combination, with the pistonV chamber,piston and valve mechanism, of means controlled by the piston andco-operating with the valve mechanism for causing the valve to admitpressure to the piston cha-mber behind the piston whenthe piston exceedsits normal forward limit of movement, for the purpose described.

11. In a pneumatic tool, an air port or passage arranged to be uncoveredby the piston when the latter exceeds its normal forward limit ofmovement, and co-operating with the valve mechanism, when so uncovered,to cause the pressure supply to be admitted to the piston chamber behindthe piston, for the purpose described.

l2. In a pneumatic tool, the combination of the piston chamber andpiston, means for resetting the piston after it has moved forward todeliver its blow to the tool, a valve .for controlling the admission ofpressure to and its exhaust from the piston chamber behind the piston,and a passage communicating at one end with the valve chamber andopening at the other into the piston chamber by a port adapted to beuncovered by the piston when the latter exceeds its normal forward limitof movement, and operating when so uncovered to cause the valve to admitpressure to the piston chamber behind the piston, for the purposedescribed.

13. ln a pneumatic tool, the combination of the piston chamber andpiston, means for resetting the piston after it has moved forward todeliver its blow to the tool, a valve for controlling the admission ofpressure to and its exhaust from the piston chamber behind the piston,means at one side of the valve for moving it in one direction, a passagecommunicating at one end with the valve chamber at the opposite side ofthe valve and at its other end opening into the piston chamber by a portadapted to be uncovered by the piston as the latter approaches itsnormal forward limit of movement, an exhaust passage communicating withthe same end of the valve chamber and opening at its opposite end intothe piston chamber by a port adapted to be uncovered by the piston asthe latter approaches the end of its return rearward movement, and anexhaust passage communicating with the same side of the valve chamberand opening into the piston chamber by a port adapted to be uncovered bythe piston when the latter exceeds its normal forward limit of movement,for the purpose described.

14:. In a pneumatic tool, the combination of the piston chamber andpiston, means for resetting the piston after it has moved forward todeliver its blow to the tool, a valve for con trolling the admission ofpressure to and its exhaust from the piston chamber behind the piston,means for exerting a constant pressure against one side of said valve, apassage communicating with the chamber at the opposite side of the valveand controlled by the piston to admit pressure to such opposite side ofthe valve when the piston approaches its forward limit of movement, acheck valve in said passage, an exhaust passage communieatin g at oneend with the space between the check valve and main valve and opening'at its opposite end into the piston chamber by a port adapted to beuncovered by the piston as the latter approaches its rearward limit ofmovement, and an exhaust passage communicating with the valve chamberbetween the check valve and main valve and opening into the pistonchamber at a point adapting it to be uncovered by the piston when thelatter exceeds its forward limit of movement, for the purpose described.

l5. In a pneumatic tool, the combination of the piston chamber andpiston, a pressure supply duct for admitting pressure to the chamber infront of thepiston, to reset the latter, a valve controlling theadmission of pressure to and its exhaust from the piston chamber in rearof the piston, a pressure supply duct for constantly admitting pressureto one side of said valve, a passage communicating with the pistonchamber and controlled by the piston for intermittently admittingpressure to the opposite side of said valve, a check valve in saidpassage, and an exhaust passage communicatin g with the space between.the check a-nd main valve and opening into the piston chamber by twoports, one adapted to be uncovered by the piston as the latterapproaches its rearward limit of movement, and the other to be uncoveredby it when it exceeds its normal forward limit of movement, for thepurpose described.

1G. In a pneumatic tool, the combination, with the handle F having thepressure supply duct G led through it, said duct having the chambers G Din said handle, the bore E intersecting said chambers and havin g thetubular casing F tightly fitted in it, said casing bein g provided withthe ports G H, the valve I fitted in said casing and having the reducedwaist portion and enlarged ends, the spring J confined in said casin gand yieldingly holding the valve in position to close one of said ports,and the lever L pivoted in the slot K in the handle and co-operatingwith the upper end of the valve I', substantially as described.

JOSEPH BOYER. lVitnesses:

EMIL WENGER, JAMES P. MAGINN.

lOO

IIO

